1. Field of the Invention
This invention concerns an electromagnetic energization system involving the generation of a stray alternating magnetic field by, preferably, discrete lengths of conductors carrying alternating current, whereby the resulting alternating magnetic field is utilized to cause synchronous rotation of a permanent magnet rotor placed within the field. The rotation of the rotor can be used to energize a mobile object, such as a miniature toy vehicle, placed in close proximity to the conductor.
2. Description of Prior Art
Stray field magnetic energization systems are known, and in particular systems for powering and controlling small mobile objects. The use of an alternating magnetic field is generally known and such systems utilize the field to cause synchronous of a permanent magnet rotor, which rotation is used to propel the mobile object. Such systems are usually associated with a fixed track or roadway for supporting the mobile object and furthermore utilize electrical coil "windings" comprising multiple coiled strands of fine wire which, when an alternating voltage is applied thereto, induce an alternating magnetic field in the vicinity of the windings. The use of such windings is conventional and frequency control systems are routinely used to vary the frequency of the alternating field induced by the winding. An illustrative example of such a prior art system can be seen in U.S. Pat. No. 4,459,438 of the present applicant.
In alternating field energization systems of the type described above, several considerations must be taken into account. The rotary speed of the permanent magnet rotor, if synchronous with the alternating field frequency, quite likely will be too high to be used in a direct drive system, when the rotor (or another element connected to the rotor) directly engages a track or other support surface via a wheel or roller to impel the vehicle. Thus, reduction gearing of some kind is usually required. The usual arrangement is simple spur gearing or the like to achieve the speed reduction.
Another consideration respecting prior art magnetic energization systems is the cost and physical size of the various components used in the systems, particularly the wire windings and the track elements, which may be multiple segments with electrical connectors providing circuit continuity between the segments. Many of the prior art systems require bulky and costly coil windings involving many lengths of fine wire mounted in each track element, for example by molding same in the track material, to generate the stray field. The losses from such windings can be considerable, and other disadvantages are readily apparent. The physical track layout is usually limited by the winding configuration and the tracks are not readily utilizable by multiple mobile objects that can be separately and independently controlled in a suitable inexpensive manner.
The present invention overcomes the disadvantages of the prior art and results in a simple, low cost magnetic energization system for miniature mobile objects, such as small toy vehicles.